Many vehicles, such as large earth moving vehicles, for example, frequently require braking systems over and above normal brakes to maintain safe and reasonable speeds while traveling down grades of various degrees and to decrease vehicle speed during vehicle operation. To this end so-called brake-saver mechanisms, in the nature of hydrokinetic brakes, have been utilized in conjunction with truck engines in vehicles.
Such structures in many instances have been complicated and comparatively expensive, and particularly as regards retarding capacities.
In applications requiring a flywheel clutch as used in many over the road trucks, cooling problems of the clutch exist, and previous designs in some instances have posed problems of expense and complex structure in the area of circuit sealing and control of retarding capacity.
In some previous structures utilizing an oil-cooled clutch, problems have occurred when the clutch is disengaged, and a clutch brake contacted to stop rotation of a clutch output member, in that high viscous drag at the clutch existed.
Hydrodynamic retarders for vehicles for effecting a selective braking thereof have previously been devised, and are currently in use by the assignee company of the present application. Apparatus of this nature is to be found in previous U.S. Pat. No. 3,352,385, Nov. 14, 1967, To Lowell E. Johnson and U.S. Pat. No. 3,490,567, Jan. 20, 1970, to Richard B. Clark et al, both being assigned to the assignee of the present application.